The present invention is directed toward a contract estimating system and more particularly toward such a system which utilizes a digitizer ruler and a digitizer board for measuring and counting the various construction components and a computer for accumulating the information.
In the building construction trades there is the necessity to provide accurate estimates of the cost of construction for use in competitive bidding. An accurate cost estimate must take into account the costs of a vast multitude of structural, plumbing, electrical, heating and other types of purchased equipment and components. Preparing accurate estimates has, in the past, been a time consuming and expensive task. This difficulty has been aggravated in recent years by the manyfold increase in the types and sizes of equipment used in modern construction and by rapidly changing prices.
Computers have been utilized in recent years to store and process the voluminous data required in the preparation of cost estimates. Such computers can easily store the pertinent data concerning the wide range of equipment from manufacturers catalogs and provide ready access to the information on demand. Furthermore, the mathematical operations required in producing a tabulation of all of the equipment for a large construction job together with any desired cost breakdown of the materials can easily be performed by the computer.
Nevertheless, human operators are required to load the data from the architect's drawings into the computer so that it may produce the desired cost estimate. The estimator must work from blueprints or drawings and insert quantity data for each type of equipment or component involved. For example, the operator, through the use of a keyboard or the like, manually inserts data relating to the number of feet of electrical conduit, the number of feet of pipe or the total number of pipe fittings of any given type and size, etc. In determining the number of feet of conduit or pipe or the like, the estimator normally utilizes a ruler to measure the component on the architect's drawing and feeds this measurement into the computer which, utilizing a scale factor, converts this measurement into the proper number of feet. The scale factor is selected by the estimator based on the drawing scale factor and is programmed into the computer.
Devices have been proposed in the past for assisting an estimator in measuring the length of conduit or pipe or the like on a drawing. These devices utilize a hand held probe which includes a small wheel mounted at the lower end thereof. The wheel is rolled along the length of line on the drawing and an electrical signal is generated which is dependent on the number of rotations of the wheel and which, therefore, represents the length of the line. This electrical signal can be fed into a calculator or computer which can be used to assist the estimator in accumulating the data and preparing a bid. Examples of such devices are shown in U.S. Pat. Nos. 3,497,959; 4,009,339; and 4,383,301.
While such devices may be of some benefit to the estimator, they fall short of being significant help. Initially, it is noted that such devices rely on friction between the wheel or roller and the drawing. If there is any slippage, an inaccurate measurement will be made. Thus, the estimator must work relatively slowly to ensure that the device is making proper contact with the drawing at all time. Furthermore, such devices can only be utilized to measure lengths of pipe or conduit or the like. They cannot be utilized to count the number of pipe fittings and numerous other components used in construction. While other input devices such as keyboards or other types of buttons can be utilized to input data relating to these various other types of components and data relating to scale factors and component sizes and the like, this greatly increases the cost and complexity of such a system thereby making it more difficult and costly for an estimator to utilize. Also, when keyboard entries are made, the chance of human error is more likely.
In Applicant's prior application Ser. No. 784,338, a system is described which utilizes a hand held probe to feed all of the relevant necessary information into the computer. The system includes a ruler divided into a plurality of equally spaced increments each of which is marked by a machine readable bar code. When the ruler is placed on a drawing, the length of a component can be measured and fed into the computer by scanning one of the ruler bar codes with the probe. A menu is also provided which includes a plurality of bar codes representing different component parts and sizes and a plurality of scale factors. While Applicant's prior system has advantages over the prior art, it also has limitations since the bar codes on the ruler cannot be placed too close together or they become too small to read with the sensor.
U.S. Pat. No. 4,578,768 describes a computer-aided digitizing system for use by an estimator which does not utilize bar codes. This system requires, however, that the plan or blueprint be small enough to be placed on a surface thereof. Thus, the system cannot be used with larger prints.